The invention relates to semiconductor opto device.
In prior art, a plurality of different semiconductor devices are known, e.g., diodes, transistors, thyristors, triacs, etc.
Diodes are semiconductors that permit current to flow in one direction.
They include two connections, namely an anode and a cathode.
If a positive voltage is applied between the anode and the cathode, the diode is operated in conducting direction—a “forward current” will then flow through the diode.
If a negative voltage is applied between the anode and the cathode, the diode locks. The current flowing in locking direction during operation of the diode (“locking current”) is in general substantially smaller than the current flowing in conducting direction during operation of the diode.
As the locking current of a diode becomes the larger the stronger the diode is exposed.
This effect is utilized for light measurement in the case of photodiodes.
Photodiodes may be incorporated in a package provided with a light-transmissive window, e.g., a glass window.
If the anode and the cathode are short-circuited in the case of a photodiode, a short-circuit (photo) current—that depends on the intensity of the exposure—will flow.
For operating a photodiode, the applying of an external voltage is thus not cogently necessary.
If a locking voltage is applied between the anode and the cathode of a photodiode, i.e. the diode is operated in locking direction, the current flowing through the diode will remain substantially unaltered. The response time of the diode will, however, be shortened since the barrier layer capacity decreases as the locking voltage increases.
Photodiodes generally supply relatively small (photo) currents only and are therefore as a rule connected to a downstream amplifier.
Photodiodes, e.g., appropriate germanium photodiodes, silicon photodiodes, etc., may be used for a plurality of different applications, for instance, in systems for the automatic switching on and off of lighting installations.
In this case, a corresponding photodiode or the photodiode and the downstream amplifier, respectively, may be connected to separate evaluation electronics.
The evaluation electronics compare the current/voltage supplied by the photodiode or the downstream amplifier, respectively, with a predetermined threshold value.
If this threshold value is exceeded, the pertinent lighting installation is switched off, so that energy may be saved.
If appropriate standard photodiodes are used in the above-mentioned systems, it is a disadvantage that the (relative) spectral sensitivity of the photodiodes is different vis-à-vis the (relative) spectral sensitivity of the human eye.
This may result in that a lighting installation controlled by such a standard photodiode is, in the case of particular spectral compositions of the light hitting the photodiode, possibly switched off “too late” (i.e. remains in a switched-on state although it is already “sufficiently bright” according to the subjective feeling of the human eye). This results in an unnecessarily high energy consumption.
Furthermore, particular other spectral compositions of the light hitting the photodiode may result in that the pertinent lighting installation is possibly switched off “too early” (i.e. already when it is in fact still “too dark” according to the subjective feeling of the human eye). This may have an adverse effect on security.
For this reason, photodiodes whose (relative) spectral sensitivity is adapted to that of the human eye are used in specific systems.
The above-mentioned separate evaluation electronics downstream the photodiode, however, result in that appropriate photodiode systems can be realized with relatively great effort and/or with relatively large dimensions only.
For these and other reasons, there is a need for the present invention.